I. Field of the Invention
The present invention relates generally to systems for tracking and monitoring transportation vehicles. More particularly, the present invention relates to a system for precisely locating and monitoring railway cars within a predetermined radius of a receiver for wireless communication.
II. Description of the Prior Art
Systems for tracking and monitoring railway cars are generally known. For example, U.S. Pat. No. 3,377,616 to J. H. Auer, which issued on Apr. 9, 1968, entitled VEHICLE IDENTIFICATION SYSTEM provides a railway car identification system in which a transducer device is mounted to a railway car. The transducer device has an electrical signal generating circuit that is rendered effective when the transducer is exposed to a light beam from a wayside station. The transducer then radiates a signal that includes a vehicle identification code of the railway car to a receiving device of the wayside station.
Similar to U.S. Pat. No. 3,377,616 above, U.S. Pat. No. 4,160,522 to D. V. Dikinis, which issued on Jul. 10, 1979, entitled AUTOMATIC CAR IDENTIFICATION SYSTEM describes another railway car identification system in which light signals are received from and transmitted to a wayside station. This patent provides a light beam-based system in which an identification label having vertical, light re-transmitting columns is attached to the side of a railway car. Each column of the identification label represents a digital number. As the railway car passes a wayside station, a light transmitter of the wayside station transmits a light beam at the identification label and a light receiver of the wayside station receives a light signal from the identification label. The light receiver then decodes the light signal and transmits all pertinent information to other data processing equipment at a remote location.
In addition to light signals, wireless signals or communication may also be used to transmit railway car identification information between a railway car and a wayside station. Such wireless communication includes radio frequency, microwave, satellite link and spread spectrum technologies. For example, U.S. Pat. No. 4,104,630 to N. E. Chasek, which issued on Aug. 1, 1978, entitled VEHICLE IDENTIFICATION SYSTEM USING MICROWAVES, provides a microwave-based system in which an identification panel is attached to the side of a railway car. To identify the railway car, a microwave signal emitted from an interrogating transmitter of a wayside station is reflected by the identification panel as a doppler offset signal. Thus, the wayside station will register that a railway car when an identification panel has passed. Also, U.S. Pat. No. 5,445, 347 to J. S. Ng, which issued on Aug. 29, 1995, entitled AUTOMATED WIRELESS PREVENTIVE MAINTENANCE MONITORING SYSTEM FOR MAGNETIC LEVITATION (MAGLEV) TRAINS AND OTHER VEHICLES provides an automated maintenance system for a MAGLEV train. Each car of the MAGLEV train includes a status unit which monitor the operational status or condition of the car. Network units at wayside stations transmit control signals which poll the status units and cause them to transmit data signals via a spread-spectrum time-division-multiple-access network. The network units relay the data signal to a maintenance control center via a wide-area-network.
Thus, the above patents provide systems for monitoring railway vehicles in which each vehicle must have vehicle transmitters and vehicle receivers in order for the system to operate properly. In particular, the vehicle transmitters are necessary to transmit vehicle identification signals to wayside receivers at local wayside stations, and the vehicle receivers are necessary to identify a local wayside station and determine when the vehicle transmitters should transmit such signals. Therefore, the cost of manufacturing, installing and maintaining the systems described in the above patents must include the such costs for both the transmitter and the receiver for each transit vehicle. In addition, each transit vehicle must have enough power to maintain the energy requirements of both the transmitter and the receiver.
The present invention provides an efficient and cost effective system for monitoring transit vehicles within a defined area of a wayside receiver. For the present invention, each transit vehicle has a vehicle transmitter but does not require a vehicle receiver. In particular, the vehicle transmitter sends vehicle information, such as transmitter specific parameters and status conditions of cargo, without regard to whether a wayside receiver is nearby. When the vehicle comes within range of a wayside receiver, the wayside receiver will periodically receive vehicle information from the vehicle transmitter and forward such information to a central database. Accordingly, the cost of manufacturing, installing and maintaining a vehicle receiver and the energy requirements for maintaining such vehicle receiver are no longer needed.